1. Field of the Invention
The invention relates to corrosion inhibitors which are amides of cyclic amidines. The inhibitors are particularly useful for preventing the corrosion of metals caused by H.sub.2 S and CO.sub.2 ("acid gas") in water-in-oil, particularly in saltwater-in-oil emulsions.
2. Description of the Prior Art
It is known to inject a solution or dispersion of corrosion inhibitors in the crude oil during oil recovery, and in the transport or storage of the crude oil so that a protective layer forms on the surface of the metal parts coming in contact with the oil. The crude oil emulsions usually contain saltwater and in many cases, depending upon the origin of the oil, contain H.sub.2 S and CO.sub.2 which have a pronounced corrosive effect. The corrosion inhibitors to be used for this purpose should be soluble in oil and should at least be dispersible in saltwater so that they can have an optimum effect.
Such systems are known from German published application No. 2,846,977. These are imidazolinium salts which are used dissolved in an oil soluble organic solvent in the presence of a hydrocarbon oil. The problems with such systems are the relatively complicated metering form (3 components) and the fact that the corrosion protection is not satisfactory in all cases. We have noted, for instance, that the imidazoline having the formula ##STR1## (as chloride) described in the referenced publication does not develop sufficient effectivness against the corrosive erosion caused by the effects of H.sub.2 S when used alone.